Downsides of downhill: The adverse effects of head vibration associated with downhill mountain biking on visuomotor and cognitive function

振动可以定义为当人体被振动表面支撑或与振动特征相互作用时，围绕一个稳定点的振荡运动。由于接触振动对健康的负面影响已引起关注，因此制定了国际和欧洲标准，以确定职业接触的阈值和风险预防。一个新出现的问题与振动从特征-身体界面转移到头部水平有关，这可能与大脑结构和功能的变化有关。大多数关于振动对人体影响的研究都是针对生理和肌肉骨骼状况的，而对振动引起的认知问题的关注相对较少。测量认知功能细微变化的困难可能是解释研究数量有限的一个因素。在自行车运动中，由于轮胎表面和地形的持续相互作用，振动是固有的活动。振动能量必须被自行车的机械结构和骑行者的软组织吸收，以保护轴骨和中枢神经系统。有人认为，公路骑行期间的振动大大超过了职业暴露限值（Edwards & Holsgrove, 2020），这表明不良健康结果的风险增加。Hurst等人在2020年提出了下坡山地自行车（DH MTB）中头部振动的负面影响的初步证据，他们发现四次DH试验足以损害执行功能的各个方面，如精神运动速度、反应时间、加工准确性和心理灵活性。虽然该研究将DH组的表现与没有头部加速度的运动匹配组和对照组进行了比较，但该研究缺乏对头部加速度的直接量化。然而，作者之前证明，DH MTB期间的旋转和动头部加速度高于足球、雪地运动、接触运动和小轮车运动（Hurst等人，2018）。假设在一个赛季的足球和冰球比赛中，重复的头部加速度可能会损害白质完整性和神经认知，那么在整个赛季中，DH车手可能面临持续不可逆转的脑损伤的风险增加。该项目的主要目的是研究与DH MTB相关的头部振动如何影响认知功能、动眼肌和身体运动控制。第二个目的是阐明振动暴露与脑功能之间的剂量-反应关系。为此，将开发一种最先进的VR模式，具有高灵敏度，可靠性和有效性，可用于早期识别脑功能障碍。通过了解头部振动的大小及其对认知健康的潜在影响，我们可以探索减少振动和减轻其有害影响的方法。

Vibration can be defined as an oscillatory movement around a stable point when the human body is supported by a vibrating surface or interacts with a vibrating feature. As the negative health effects of exposure to vibration have become a cause of concern, international and European standards have been developed to define thresholds and risk prevention in occupational exposure. An emerging issue is related to the transference of vibration from the feature-body interface to the level of the head that might be associated with changes in brain structure and function. Most studies investigating the effects of vibration on the human body are directed at physiological and musculoskeletal conditions, and relatively little attention has been given to vibration-induced cognitive problems. Difficulties of measuring subtle alterations in cognitive function might be one factor that could explain the limited number of studies.In cycling, vibration is intrinsic to the activity due to the continuous interaction of the tyre surface and the terrain. Vibrational energy must be absorbed by mechanical structures of the bike and the cyclists' soft tissues to protect the axial skeleton and the central nervous system. It has been suggested that vibration during road cycling substantially exceeds occupational exposure limits (Edwards & Holsgrove, 2020), which indicates an elevated risk of adverse health outcomes. Initial evidence of the negative effect of head vibration experienced in downhill mountain biking (DH MTB) has been presented by Hurst et al, 2020 who found that four DH trials were sufficient to impair aspects of executive function such as psychomotor speed, reaction time, processing accuracy, and mental flexibility. Although the study compared the DH group's performance to an exercise-matched group without head accelerations and a control group, the study lacked direct quantification of head accelerations. Nevertheless, the authors previously demonstrated that rotational and translational head accelerations during DH MTB are higher than those reported in soccer, snow sports, contact sports and BMX (Hurst et al., 2018). Provided that repetitive head accelerations could compromise white matter integrity and neurocognition over the course of a season in football and ice hockey, DH riders might face an increased risk of sustaining irreversible brain injuries over an entire race season. The primary aim of the project is to investigate how head vibrations associated with DH MTB influence cognitive function, oculomotor, and body movement control. A secondary aim is to elucidate the dose-response relationship between vibration exposure and brain function. For this purpose, a state-of-the-art VR paradigm will be developed, with high sensitivity, reliability, and validity for early identification of brain dysfunction. By gaining knowledge on the magnitude of head vibration and its potential influence on cognitive health, we can explore ways to reduce vibration and mitigate its harmful effect.